In the prior art, it is often needed to have liquid aerated.
For example, in the biological treatment of waste water (such as industrial waste water or household sewage), waste water often needs to be aerated, so as to provide with oxygen to the aerobic micro-organisms in the waste water. The micro-organisms are able to absorb, adsorb and oxidize the organic contaminants carried in the waste water, and decompose them to some simple inorganic materials such as oxidized carbon, water, sulfate, nitrate etc., that is, turn the toxic and harmful matters into non-toxic and harmless matters, so that the waste water is purified.
In aquaculture, if the content of oxygen dissolved in water is lower than 4 mg/L, fishes would hardly keep living, thus, it is necessary to add oxygen into the water providing with the essential oxygen for fishes' living. Less oxygen dissolved in the water indicates higher water pollution, and so it is more necessary to supply oxygen into the water.
Moreover, in the fields of food, pharmacy, chemical industries, etc. it often needs to add gas into liquids. In various applications, liquid is not only limited to water, and gas is not only limited to oxygen or air either.
However, in the existing technology, air is normally injected into liquids by means of a blower. As for the widely used biological treatment of waste water, the use of a blower would consume great amount of energy such as electricity, and would also cause environment pollution. In addition, using a blower to inject air directly into liquid, the oxygen dissolved in the liquid is very limited; instead, most of the air injected would be directly escaped from the liquid.